Hi Richard: Thanks for yet another detailed description regarding aspects of this confusing topic.
My conclusion from all this discussion is that the only practical difference between the 6.1.2.2 text in the main body of EN 60950-1 and the text in Annex ZB is that for Finland, Norway, and Sweden, equipment that uses a permanently connected earthing conductor must be installed by a service person. The text in the main body leaves open the possibility that the protective earthing conductor could be installed by the user. I don't know why they couldn't state the difference more simply. A related conclusion is that for "typical" office equipment, surge protectors from tip/ring to ground must have a minimum breakover of 400 volts in Finland, Norway, and Sweden unless the equipment is intended to be installed by a service person. I do have one remaining question. You mention that EN60309 describes pluggable Type B sockets. I do not have a copy of EN60309. It is true that the standard AC mains plugs commonly used on home and office ITE products are completely incompatible with the ones defined in EN60309? I would just like to know if there is any opportunity for a manufacturer to argue that the plug on their standard office ITE product is actually intended for a Type B socket. Thanks again for your help with sorting all this out. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected] http://www.randolph-telecom.com > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Richard Hughes > Sent: Friday, January 09, 2004 9:47 AM > To: Joe Randolph > Cc: [email protected] > Subject: RE: EN60950-1,TNV to Earth Insulation > > > > Joe, > > Following fast on the heals of my earlier reply, you can perhaps > understand that equipment that is professionally installed is > expected > to be earthed if required (otherwise the installer could hardly be > called 'professional'!). > > Similarly, it is expected that an industrial socket to EN60309 > (pluggable Type B) will be installed so that its earth connection is > connected to the building's earth. > > Point 3 is for the Central Office of telecoms centres. > Again, in such > premises it is expected that a 'proper' earth connection will be > available. For equipment powered from station office > batteries, this is > generally a sub-set of 1. > > Point 4 is not applicable in Europe, as can be seen by looking at EN > 60950-1 clause 6.1.2.2, where you will see that it has been > removed as a > Common Modification. Basically, it is considered that a label on the > equipment telling the user to get the equipment > professionally installed > does not provide an adequate degree of safety (due to the > likelihood of > such a notice being disregarded). > > I hope that this is now the end of this topic, but if not I'm > more than > happy to provide PAID consultation!!! > > Regards, > > Richard Hughes > www.safetyanswers.ltd.uk > > > > Joe Randolph wrote: > > > > > In a posting dated 1/8/2004, I wrote: > > > > > Now I go to Annex ZB and look at the deviations to > clause > > 6.1.2.2 for Finland, Norway, and Sweden. The > exclusions > > described here are much more restrictive, > limited to > > permanently connected equipment or pluggable > equipment type > > B, used in restricted access locations > where equipotential > > bonding has been applied. In other > words, a telephone > > central office or *maybe* the main > telephone closet in an > > office building. Certainly, no > stretch of the imagination > > would have this clause > include the typical office environment. > > > Hello All: > > > Okay, I re-read the wording of the Annex ZB deviation to > clause 6.1.2.2 > of EN 60950-1, and I think I have developed > a partial answer to my own > question. I see that I missed > the word "and" in one place and perhaps > misinterpreted the > meaning of "and" in a second place. After reading > the > clause carefully several times, I think it is saying that > exclusions > are available for four separate cases: > > 1) > Permanently connected equipment. > > 2) Pluggable equipment > Type B. > > 3) Equipment used in a restricted access > location that has equipotential > bonding. > > 4) > Equipment that has provisions for a permanently connected > protective > earthing conductor and is provided with > instructions for installation of > that conductor by a > service person. > > > In the wording of Annex ZB, note > that the "and" between cases 3 and 4 > could be interpreted > to be merging them into a single case, rather than > > establishing case 4 as a standalone case. > > So, the > liberal interpretation is that case 4 is a viable, standalone > > option, similar to the 6.1.2.2 text in the main body of > the standard > except for the specific reference to having a > service person install the > ground conductor. Even with > the reference to the service person, this > case provides > enough wiggle room to allow the equipment to be used in a > > normal office environment. > > The conservative > interpretation merges cases 3 and 4 into a single case > and > pretty much excludes the normal office environment if the AC > mains > connector is pluggable Type A. > > I'm still > interested to know what other list members think this means > > for the case I described in my earlier posting. > > > > > Joe Randolph > Telecom Design Consultant > Randolph > Telecom, Inc. > 781-721-2848 (USA) > > [email protected] > http://www.randolph-telecom.com > > > > > ------------------------------------------- > > This message is from the IEEE EMC Society Product Safety > > Technical Committee emc-pstc discussion list. > > > > Visit our web site at: http://www.ieee-pses.org/ > > > > To cancel your subscription, send mail to: > > [email protected] > > with the single line: > > unsubscribe emc-pstc > > > > For help, send mail to the list administrators: > > Ron Pickard: [email protected] > > Dave Heald: [email protected] > > > > For policy questions, send mail to: > > Richard Nute: [email protected] > > Jim Bacher: [email protected] > > > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc > > > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ieee-pses.org/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
